The chief goals of the proposed research are to characterize the interaction of currently available marker dyes with the blood-ocular barriers and to identify additional fluorescent dyes that define selectively the specific barrier and transport characteristics of the eye. Fluorescein, as previously noted in the non-ophthalmic literature and recently confirmed by us, has a relatively high lipid permeability. We seek fluorescent compounds with low protein-binding affinity which are sufficiently lipid insoluble that movement across the blood-ocular barriers will identify specific permeability or transport characteristics. We also seek protein-bound dyes to provide data about barrier integrity to large molecules. For each dye, we plan to study the spectral characteristics, the lipid solubility as reflected by the partition ratio, and the binding to plasma proteins as determined by equilibrium dialysis. We shall then study the intraocular tissue distribution of suitable dyes after intravenous injection using quantitative epi-fluorescence microscopy, a technique with sufficient resolution to evaluate cell-to-cell differences. To study transport phenomena, we shall measure tissue dye distribution with quantitative epi-fluorescence microscopy after in vitro incubations with dye of both anterior segment and posterior segment tissues; and we also shall conduct traditional uptake studies using radiolabelled dyes. Promising dyes will be studied after intravenous injection in animal disease models that may be associated with a blood-ocular barrier defect. Collaborative arrangements will be made for aqueous and vitreous fluorophotometry using promising dyes, and limited toxicity studies are planned using particularly promising dyes. We hope that any new dyes identified will provide greater specificty than fluorescein in clinical diagnosis and experimental work and will yield further information about the underlying pathophysiology of human disease.